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Old Nov 15, 2005, 07:35 PM
HeliAP'er!
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Surrey, UK
Joined Aug 2003
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PCM or Dual Conversion PPM?

Hi all,

Just wondering what's the preferred option in the electric heli world for receivers - Dual Conversion PPM or PCM?

The prices are pretty similar ...

Ta muchly,


David
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Old Nov 15, 2005, 08:10 PM
Our Daddy and Heli Junkie
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In Heli Wonderland
Joined Aug 1999
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PCM, programmed crash mod.

I use PPM (FM) both dual and single conversion, few issues.

But I hear many funny things about the 35mhz freq in the UK.

JMHO
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Old Nov 15, 2005, 08:40 PM
-Flight enthusiast_
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Lake Louise, AB, Canada
Joined Feb 2000
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Quote:
Originally Posted by Fred Bronk
PCM, programmed crash mod.
=> old wive's tale in this day and age

Hi Fred!

Glen
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Old Nov 15, 2005, 08:42 PM
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San Carlos, California, United States
Joined May 2002
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I tend to use PPM (FM) as well.

I've had lockouts on PCM and they scare me. If there's interference, I want to know about it so I can bring down the heli before I fly it out too far and it becomes worse.

Toshi
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Old Nov 15, 2005, 08:59 PM
HeliAP'er!
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Surrey, UK
Joined Aug 2003
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Wow, you guys are fast!

I was thinking about the failsafe in PCM too ... it's all too easy to let the PCM lull you into a false sense of security as to how much interference you're actually picking up. Not glitching is one thing, but not glitching because the heli is flipping sitting in failsafe, under no control of your own, is quite another!

I've heard that the Futaba 138DP is a good'un .... anyone against that?

Many thanks!


David
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Old Nov 15, 2005, 08:59 PM
Aerial Shutterbug
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San Mateo, California, United States
Joined Nov 2001
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I use PCM with no programmed failsafe settings.

Of course with my prior experience with PPM systems, I've come to the conclusion that either system have a common guarantee...that is they always will lead you to the crash site.

I also try to stay with the factory antenna if at all possible.

-Roger
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Old Nov 15, 2005, 09:04 PM
-Flight enthusiast_
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Lake Louise, AB, Canada
Joined Feb 2000
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Quote:
Originally Posted by TMorita
I tend to use PPM (FM) as well.

I've had lockouts on PCM and they scare me. If there's interference, I want to know about it so I can bring down the heli before I fly it out too far and it becomes worse.

Toshi
Hi Toshi,

The term "lockout" is misleading, I think. I ask, would you rather the heli had a seisure during the period of interference? Myself, I much prefer zero throttle, neutral controls, and slightly negative pitch, which causes the heli to rear up from FFF and then settle downward. Now, some older models of some brands of PCM receivers apparently did have trouble resuming control, but again I believe that is old news. JR works great and I did do a lot of "field testing" with my first LOGO 20 back in 2000. There was something that caused it to glitch and the PCM setup worked very well, time after time.


...... Oh no - another PCM debate thread

Cheers!

Glen
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Old Nov 15, 2005, 09:07 PM
Deletedfor proving Nauga wrong
Joined Mar 2005
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If you didn't set the failsafes... the factory did... If the RX has failsafe I can aalmost guarantee that it will use either the "Hold last" or the preprogrammed position even if you failed to set them up. I know of no RX with failsafe that does not automatically use them.

So if you have PCM (or one of the newer PPM RX's with failsafes...) and you fail to think about the failsafes, you are most likey ACCEPTING the factory default (which is usually "Hold last") If the default leaves you at high throttle with some mix if stick inputs... that heli is going to move out in some direction... most likely a direction YOU DON'T WANT!

If you have failsafes, AT A MINIMUM set the throttle failsafe. It normally has a low RX voltage trigger in addition to theloss of coherant signal trigger. And its most likely a good idea on the heli to choos a high idle which will allow a semi-contrlled descent with power... then you can put it to full + collective and let the fuel burn out if its triggered on low voltage.
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Old Nov 15, 2005, 09:44 PM
TC
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Hogster
heres an interesting artical on the subject
the title says it all

Everything You NEVER Wanted To Know About Radios !
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Old Nov 15, 2005, 09:45 PM
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Australia, NSW, Cherrybrook
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I use the Mutiplex DS IPD Recievers which are Dual Conversion PPM with IPD and Failsafe.

They supposedly give you the best of both worlds.

I can say that i've never suffered from interference or glitching of any kind.
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Old Nov 15, 2005, 10:18 PM
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If you are considering getting into aerial photograohy maybe consider the fma recievrs as a first purchase and then you can add on thier copliot systems when bucks start rolling in .
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Old Nov 16, 2005, 12:14 AM
Our Daddy and Heli Junkie
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Glen, I knew that would get you up

Sure, PCM as well as ISP has come a long way just like EP.

Now I use a few of the Bergs with IPS, sort of a poor mans PCM as it will only recognize your TX signal.

But no matter would you use don't let it hide problems, let it protect you from things you have no control over.

FB
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Old Nov 16, 2005, 01:25 AM
1.21 Gigawatts!
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Joined Oct 2000
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The system has to be proven clean with a PPM receiver before a PCM receiver should be used. Using any system to cover up the glitch is bad practice.

I would trust my helis only to PCM receivers. I had one very close call with PPM equipped heli that scared me. Some idiot turned on his radio while I was flying. If only I had PCM the heli would have shutoff and crashed in the field instead of flying toward crowd of people.
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Old Nov 16, 2005, 01:26 AM
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Cape Town, South Africa
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Go with a PPM receiver that has some kind of DSP (with failsafe). I've heard only good things about Multiplex's IPD receivers. Hopefully the new Bergs will be good. FMA have DSP PPM receivers too.

Why would anyone want to use PCM and be restricted to a single brand?
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Last edited by aragon; Nov 16, 2005 at 01:33 AM.
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Old Nov 16, 2005, 01:46 AM
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United States, FL, West Palm Beach
Joined Jun 2001
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Hello

Fred is correct don't hide interference sources that may be caused by your helicopter. Fish any problems out using a PPM Rx. Switch to PCM after you figure out your heli is glitch free.

Trust me on this you dont want a stray hit affect your electronics when your hovering inverted right off the deck with a heli spinning 2000 rpm at the head. I fly PCM on everything(I even had on a Piccolo Pro).

Carlo
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